In order to prevent children from watching inappropriate audiovisual contents, several technical solutions have been proposed in the past. One solution consists in adding a logo superimposed on the video so as to indicate to the viewer the possible offensive nature of the content he is going to watch. The logo can indicate a rating according to a rating system, such as the Motion Picture Association of America rating System (MPAA) for example. However, whatever the precision of the adopted rating system, as a normative system, not all people would give the same rating to the same audiovisual content, because people have different sensitivities. Moreover, the rating system is nothing more than a least common denominator. Ideally, the parent should watch the whole audiovisual content before to form an opinion on whether the audiovisual content is appropriate for his children. The problem is that it takes much time, which makes this solution not realistic. It shows however how much the audiovisual content itself is important to rate the audiovisual content. Based on the common saying “An image is worth a thousand words”, another solution, described in the patent U.S. Pat. No. 6,684,240, consists in setting parental lock levels based on example content. An example extracted of the audiovisual content 102 is shown to the user, and, based on that example, the user decides to block the watching of the audiovisual content or not. When the audiovisual content contains in its metadata a rating, then this rating is retained for future use. When a further audiovisual content having a similar rating is broadcast, this audiovisual content is automatically blocked. This solution has the advantage that the parent does not need to know the signification of the ratings, which may be numerous and complicated, because the example content has shown him directly this signification. It may however happen that two audiovisual contents similarly rated by a rating system, for example on a violence scale, are perceived differently by the same person. It may also happen that the audiovisual content is not rated at all. In such cases, the parent has to come back to the old solution consisting in watching the whole audiovisual content, but again, the parent has no time for that. In the end, the parent has to choose between two solutions, either watching the whole audiovisual content to form an opinion, or relying on a relatively unreliable rating system.